A hearts and arrows pattern is successfully generated from within a round cut diamond when exposed to light, provided that the round diamond is cut into a nearly perfect round shape possessing equal and symmetrically cut facets with its angular proportions polished within relatively narrow ranges, as taught below in Table I. The symmetry of a near perfect round cut diamond provides brilliance, color and optical light handling properties which have not been matched in the marketplace by any other shaped diamond to date. Although diamonds are typically cut into many different geometrical shapes other than round such as, for example, a heart shape, oval, pear, marquis, princess, emerald, etc., only the round cut diamond has a nearly perfect symmetrical shape. It is widely believed in the diamond industry that all crown and pavilion facets should be cut with exact angle degrees and preferably with the angle differences between all pavilion angles smaller than 0.3°, the angle tolerance between the four main crown facets smaller than 0.4° and the angle tolerance for the four subsidiary crown facets smaller than 0.3° if a hearts and arrows pattern is to be achieved. This rational lies behind the belief in the diamond industry that it is impossible to obtain a hearts and arrows pattern on any shape other than round since only the round shape with its perfect symmetry can be cut to satisfy symmetrical angular tolerances with perfectly equal polished facets and without much difficulty. Since an oval shaped diamond has, by definition, a non-symmetrical geometry with two very long sides and two short sides, obtaining a hearts and arrows pattern in an oval shaped diamond contradicts conventional thinking. Moreover, oval shaped diamonds are traditionally cut using the same angle degrees on the main crown facets and a very wide range of pavilion angle degrees. Accordingly, following tradition makes it impossible to create a hearts and arrows pattern in an oval shaped diamond.
In a round cut diamond, the hearts and arrows pattern appears only when the requirements for its cut facets, angle parameters and alignment relationships are as shown in the following Table 1:
TABLE 1The shape of the diamond is perfectly symmetrical8 main crown and 24 subsidiary crown facets8 main bottom and 16 subsidiary bottom facetsAll main facets (crown & bottom) have to be polished at a perfect 45°angel to each otherAll facets are perfectly alignedAll the bottom main facets are of equal size and at an angle rangingfrom 40.6°-41.0°All the bottom subsidiary facets are of equal size and at an angel whichis exactly 1.2° steeper than the main facets (main bottom angle40.6°-41.0° + subsidiary 41.8°-42.2°)All the main crown facets are of equal size and at an angle rangingfrom 33.8°-35.1°. They have to be perfectly aligned on the mainbottom facets.All the subsidiary crown facets are of equal size and perfectly alignedon the main crown and subsidiary bottom facets and polished at anequal angle.The ideal cut proportions are:total depth 59.4%-62.4%crown height 14.5%-16.0%girdle thickness 1.5%-2.95%Roundness 99.0%-100%Table size: 53.0%-57.5%